GlusterFS: set correct filename when cloning volume

When cloning a volume, the volume[name] field was populated
with incorrect data, resulting in an unexpected filename containing
the volume data.  This results in failures of later operations on
that cloned volume.

(cherry picked from commit bfb66019edd197141ea1462ba78dd27a2ed0e40d)

Resolves: rhbz #1023065

Upstream-Havana: https://review.openstack.org/#/c/53897/
Upstream-Icehouse: https://review.openstack.org/#/c/53735/
Launchpad Bug: #1244238
Change-Id: I067ed44cebdc8e91e9ded326953fd0c99d003f05